Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending  

双腔铝型材力控制模式拉弯条件下的截面畸变及回弹特性

作　　者：Zhi-wen LIU Zi-xuan DONG Cong-chang XU Jie YI Luo-xing LI 刘志文;董子轩;徐从昌;易杰;李落星(南华大学机械工程学院,衡阳421001;湖南大学整车先进设计制造技术国家重点实验室,长沙410082)

机构地区：[1]School of Mechanical Engineering,University of South China,Hengyang 421001,China [2]State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle,Hunan University,Changsha 410082,China

出　　处：《Transactions of Nonferrous Metals Society of China》2024年第8期2476-2490,共15页中国有色金属学报（英文版）

基　　金：the National Natural Science Foundation of China(Nos.52005244,U20A20275);the Natural Science Foundation of Hunan Province,China(Nos.2021JJ30573,2023JJ60193);the Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,China(No.31715011)。

摘　　要：3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.采用显−隐式混合方法建立了用于模拟双腔铝型材力控制模式拉弯工艺成形过程的三维弹塑性有限元模型。考虑到计算的准确性和效率,给出了有限元建模中各种数值参数和算法的最优选择。揭示了型材拉弯截面畸变和回弹的形成机理,系统研究了预拉伸、补拉伸、摩擦和添加内填充物对弯曲成形质量的影响。结果表明,铝型材拉弯时的应力状态为单轴环向应力。应力沿型材长度方向分布不均匀,且最大拉应力位于离型材中心一定距离的位置;随着型材逐渐包覆到弯曲模具上,沿型材长度方向的截面畸变分布特征由V形转变为W型。成形工具卸载后,由于应力释放截面畸变明显减小,卸载前后畸变最大差值为13%。随着预拉伸力和补拉伸力的增加,截面畸变逐渐增加,而回弹先减小后保持不变。增加弯曲模具与型材间的摩擦,截面畸变略微减小,但回弹增大。往型材型腔中添加PVC填充物,型材拉弯截面畸变减小了83%,但回弹增大了192.2%。

关 键 词：hollow aluminum profile force controlled stretch-bending numerical parameters springback analysis approach cross-section distortion SPRINGBACK process parameters 

分 类 号：TG146.21[一般工业技术—材料科学与工程]